title: Histological considerations of the cleavage plane for preservation of facial and cochlear nerve functions in vestibular schwannoma surgery.
abstract: OBJECTIVE
  The authors analyzed the tumor capsule and the tumor-nerve interface in vestibular schwannomas (VSs) to define the ideal cleavage plane for maximal tumor removal with preservation of facial and cochlear nerve functions.
  
  
  METHODS
  Surgical specimens from 21 unilateral VSs were studied using classical H & E, Masson trichrome, and immunohistochemical staining against myelin basic protein.
  
  
  RESULTS
  The authors observed a continuous thin connective tissue layer enveloping the surfaces of the tumors. Some nerve fibers, which were immunopositive to myelin basic protein and considered to be remnants of vestibular nerve fibers, were also identified widely beneath the connective tissue layer. These findings indicated that the socalled "tumor capsule" in VSs is the residual vestibular nerve tissue itself, consisting of the perineurium and underlying nerve fibers. There was no structure bordering the tumor parenchyma and the vestibular nerve fibers. In specimens of tumors removed en bloc with the cochlear nerves, the authors found that the connective tissue layer, corresponding to the perineurium of the cochlear nerve, clearly bordered the nerve fibers and tumor tissue.
  
  
  CONCLUSIONS
  Based on these histological observations, complete tumor resection can be achieved by removal of both tumor parenchyma and tumor capsule when a clear border between the tumor capsule and facial or cochlear nerve fibers can be identified intraoperatively. Conversely, when a severe adhesion between the tumor and facial or cochlear nerve fibers is observed, dissection of the vestibular nerve-tumor interface (the subcapsular or subperineurial dissection) is recommended for preservation of the functions of these cranial nerves.
authors.affiliation: Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. tsasaki@ns.med.kyushu-u.ac.jp
authors.forename: Tomio
authors.initials: T
authors.lastname: Sasaki
authors.forename: Tadahisa
authors.initials: T
authors.lastname: Shono
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Hashiguchi
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Yoshida
authors.forename: Satoshi O
authors.initials: SO
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D003056:Cochlear Nerve / Q000033:anatomy & histology*; D005154:Facial Nerve / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods*